Lash adjusting mechanism for the operating train of a reciprocating member



Dec. 3, 1968 w. J. PASK 3,413,964 LASH ADJUSTING MECHANISM FOR THE OPERATING TRAIN OF A RECIPROCATING MEMBER Filed May 9, 1967 FIG. .L

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WILL /AM J. PASK INVENTOR.

AT7URNEVS United States Patent Office 3,413,964 Patented Dec. 3, 1968 LASH ADJUSTING MECHANISM FOR THE OPERATING TRAIN OF A RECIPROCAT- ING MEMBER William John Pask, Hornchurch, Essex, England, assignor to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Filed May 9, 1967, Ser. No. 637,130 Claims priority, application Great Britain, Oct. 21, 1966,

7,241/ 66 5 Claims. (Cl. 123-90) ABSTRACT OF .THE DISCLOSURE This mechanism comprises a tappet having external and internal members threadably engaging each other. The ring gear of an epicyclic gear train is formed on an inner surface of the exterior member and the sun gear of the train is formed on the interior member. Meshing a pinion gear with the ring and sun gears and rotating the pinion gear adjusts the effective length of the tappet and thereby adjusts the lash in the operating train.

Summary of the invention Adjusting the lash in the valve train of an engine having an overhead camshaft is diflicult because of the limited space available for adjusting mechanisms. Various embodiments of the mechanical systems used to adjust the lash of conventional engines having the camshaft in the engine block have been adapted to overhead camshafts, but these systems have proved to be costly and bulky.

This invention provides an inexpensive and compact adjusting mechanism for an operating train that converts rotational motion of a camshaft into reciprocating motion of a reciprocating member. The mechanism is useful particularly in the valve train of an engine having the calmshaft and the valve on the same side of the combustion chamber, such as overhead camshaft engines having overhead valves, where space is at a premium. In the operating train, the lash adjusting mechanism of this invention comprises an exterior member having an opening therein with internal screw threads and ring gear teeth in the opening. An interior member having external screw threads and sun gear teeth is located in the opening so its screw threads threadably engage the internal screw threads and its sun gear teeth are adjacent the ring gear teeth. One of the members is contacted by the camshaft and the other contacts the reciprocating member. The ring gear teeth and sun gear teeth form part of an epicyclic gear train which is completed by a pinion gear attached to an adjusting tool. When adjustment is desired, the pinion gear is meshed with the ring and sun gear teeth and rotation of the adjusting tool produces relative rotation of the members to adjust the efiective length of the mechanism. After adjustment the members are locked relative to each other by a spring washer, for example.

Brief description of the drawing FIGURE 1 of the drawing is a sectional view through the valve train of an internal combustion engine having an overhead camshaft and overhead valve showing the mechanism of this invention positioned between the camshaft and the stem of a reciprocating valve. FIGURE 2 is a partial view taken in the direction of arrow 2 in FIGURE 1 showing the pinion gear of the adjusting tool meshing with the gear teeth of the adjusting mechanism.

Detailed description A cam 10 integral with an overhead camshaft 11 bears on a tappet 12 which in turn bears on a valve stem 13 so rotation of camshaft 11 is translated into reciprocation of the valve. Tappet 12 comprises an interior member 14 having a fiat upper surface 15 bearing against the cam 10 and an exterior member 16 having a boss 17 bearing against the stem. A spring retainer 18 is locked on stem 13 and a valve spring 19 bears on retainer 18 in the conventional manner.

A depending skirt 20 formed on member 14 carries an external screw thread 21 that threadably engages an internal thread 22 formed in an opening in member 16. In an annular gap 24 above the screw threads 21 and 22 and between members 14 and 16 there is an annular spring washer 25. Washer 25 is compressed between a shoulder 26 on member 14 and an annular retainer 27 positioned in a groove under gear teeth 29 in member 16. Spring washer 25 exerts a force on screw threads 21 and 22 to lock members 14 and 16 of the tappet against relative rotational movement. This force is in the same direction as the force applied to member 14 by cam 10 so there is no tendency for members 14 and 16 to rotate relative to each other during engine operation.

At the upper end of gap 24 member 14 carries a set of suntype gear teeth 28. Also at the upper end of the gap 24, member 16 carries a set of ring-type gear teeth 29. These gear teeth are best seen in FIGURE 2. The purpose of these gear teeth is to permit adjustment of the effective length of tappet 12, and thereby adjust the clearance in the valve operating mechanism, by rotating members 14 and 16 relative to each other.

This adjustment is effected by an adjusting tool having a head in the form of a small planet gear 31. Gear 31 is inserted into gap 24 to mesh with teeth 28 and 29, thereby completing the epicyclic gear train. Rotation of gear 31 then produces relative rotation of members 14 and 16. To adjust the clearance to the correct value a feeler gauge with a thickness equal to the desired clearance is inserted between the stem and the tappet. The adjusting tool is then inserted between the gear teeth 28 and 29 and is rotated until the feeler gauge is a sliding fit between the cam and the tappet. The feeler gauge and adjusting tool are then removed and the engine is operated with the desired amount of lash in the valve train.

To increase the area of the surface contacted by cam 10, tappet 12 is inverted and a smooth surface is formed on the top of exterior member 16. Cam 10 then contacts this smooth surface. An appropriate boss formed on interior member 14 then contacts valve stem 13. Gap 24 opens on the valve side rat-her than the cam. side of tappet 12 in this construction and the adjusting tool is inserted to mesh gear 31 with teeth 28 and 29 at the valve side.

Thus this invention provides a space saving lash adjusting mechanism useful wherever rotational motion of a camshaft is being converted into reciprocating motion of a reciprocating member. The mechanism is particularly useful in the valve train of overhead camshaft engines having over-head valves.

What I claim is:

1. In the operating train for converting rotational motion of a camshaft into reciprocating motion of a reciprocating member, a lash adjusting mechanism comprising an exterior member having an opening therein with internal screw threads and ring gear teeth in said opening,

an interior member having external screw threads in threaded engagement with said internal screw threads and sun gear teeth adjacent said ring gear teeth, one of said members contacting the camshaft and the other contacting the reciprocating member, said gear teeth being arranged so meshing a pinion gear therewith completes an epicyclic gear train and rotating said pinion gear adjusts the effective length of said adjusting mechanism.

2. The operating train of claim 1 comprising locking means for preventing relative rotation of said members when said pinion gear is removed.

3. The operating train of claim 2 in which the locking means comprises a spring lock washer interposed between the members.

4. The operating train of claim 3 in which the camshaft is an overhead camshaft of an internal combustion engine having an overhead valve.

5. The operating train of claim 1 in which the camshaft is an overhead camshaft of an internal combustion engine having an overhead valve.

5 References Cited UNITED STATES PATENTS 1,614,749 1/1927 Manville 123--90 3,002,508 10/1961 Barker et a1. 123-90 10 FRED C. MATTERN, JR., Primary Examiner.

F D. SHOEMAKER, Assistant Examiner. 

